Steam-pressure gkage



E. G.v ALLEN..

Steam Gage.

Patented Oct. 27 1857.

W/ INKS-SIS UNITED STATES PATENT OFFICE.

E. G. ALLEN, OF BOSTON, MASSAGHUSETTS, ASSIGNOR TO HENRY O. ALLEN, OFMALDEN, MASSACHUSETTS.

STEAM-PRESSURE GAGE.

To all whom it may concern:

Be it known that I, E. G. ALLEN, of Boston, in the county of Suffolk andState of Massachusetts, have invented certain new and usefulImprovements in Steam-Gages, and that the following description, takenin connection with the accompanying drawings, hereinafter referred to,forms a full and exact specification of the same, wherein I have setforth the nature and principles of my said improvements, by which myinvention may be distinguished from others of a similar class, togetherwith such parts as I claim and desire to have secured to me by LettersPatent.

The figures of the accompanying plate of drawings represent myimprovements.

Figure 1, is a plan or top view of my improved steam gage with the ovalplate removed. Fig.- 2 is a transverse vertical section of the sametaken in the plane of the line A B, Fig. 1. Fig. 3 is a detail view tobe hereinafter referred to.

In a spring steam gage it is very essential that the spring upon whichthe steam acts should be held perfectly firm in order to accuratelyindicate the pressure, for as the motion of the spring is largelymultiplied on the shaft of the indicator, any little varia tion in theplay of the spring would produce a greatly increased variation at theindicator, and cause an incorrect register of the pressure. It is alsovitally essential that the elastic force of the spring should be allowedto act freely and without friction. These two desirable features aresecured by my improvements, the first desideratum being effected byusing a volute spring, the peculiar construction of which will behereinafter described, and holding its outer coil between twobox-couplings rigidly screwed together, so as to prevent play in anydirection, while the second requisite is obtained by leaving the wholeof the spring, except the outer coil thus held, perfectly free to act, adisk of rubber or other elastic substance being so arranged in thebox-couplings, as to communicate the pressure of the column of steamequally to every part of the spring. 7

Another feature of my improvements consists in the adjustment of theindicating lever, by changing the length of one arm, and varying inconsequence the leverage and the degree of movement transmitted from thespring to the indicator, whereby the gage can be easily corrected incase of error, adapted to high or low pressure engines, or to heavy orlight weights, without varying the construction of the gage.

a a in the drawings represents the box in which the devices whereby themovement of the spring is transmitted to the indicator are placed, thedial plate being removed.

5 b is a volute spring, Figs. 2 and 3, placed in two box-couplings 0 andd. These couplings are firmly screwed together, a shoulder e of thecoupling cl being thus brought to bear upon the outer coil of thespring, and holding it rigidly, so as to prevent any play or frictionbetween the spring and the boxcouplings, while at the same time theremaining portion of the spring is left perfectly free to act. Thevolute spring I? b is of peculiar shape, as it has an increasing widthand thickness, as shown in Fig. 3, from its center to its circumference.By giving the spring this peculiar shape it will receive at all times,very nearly the same degree of play or movement from a stated number ofpounds pressure, at whatever degree of compression of the spring, theaddition of the said number of pounds pressure be applied. The outercoil of the spring being held by the shoulder e of the coupling (Z, theinner or smallest coil is positioned to a central short shaft or pistonf.

Steam is admitted through the short tube 9, forming a part of thebox-coupling c, and in order that the pressure of the steam may beexerted equally upon all portions of the spring 6 b, a disk or diaphragmof rubber h, Fig. 2, or other suitable elastic material is insertedbetween and held by the two box-couplings 0 and (Z, in such a manner asto entirely cover the rear surface of the spring.

From the foregoing description it will be seen that by the manner ofholding the spring in place by its outer coil, by means of twobox-couplings screwed together, there is no possibility of any play orfriction between the spring and the devices by which it is held inplace, while at the same time, the remaining portion of the spring isleft entirely free to act. The importance of these results will beapparent from the statements hereinbefore made.

I will next proceed to describe the devices which form the medium forcommunicating the movement of the spring, produced by the pressure ofthe steam, to the indicator 71 i, upon which screWt-hread the nut is canbe turned in either direction for the purpose of lengthening orshortening the rod '5 2'. The rod 2' 2' is attached by a pivot joint Zto a short arm m, attached to the sector shaped arm n, (turning upon ahearing at 0) by a set screw Thus the connecting rod 2' i and arm m,form the long arm of a lever of Which the sector shaped arm n is theshort arm and 0 the fulcrum. By means of the screw j the arm mcan be setat any desired angle With the sector shaped arm n, as shown in Fig; 1,thereby, (the rod 2' i being lengthened or shortened accordingly, asbefore explained) increasing or diminishing at pleasure the lever powerbrought to bear upon the indicator. The end of the sector shaped arm nterminates in a geared are 79, that engages With a pinion g retracted bya coiled spring 41. The pinion g is attached to the spindle 8 upon Whichis fastened the indicator 25.. From this description it will, be seenthat'the movement of the volute spring I) Z) is imparted to theindicator through the lever z, m, nand pinion q, and that the play ofthis lever,Which controls the adjustment .of the indicator whereby thegage is readily corrected in case of error, andvalso adapted to alldegrees of pressure,is made greater or less, by changing the position ofthe arm m, and turning the nut in in either direction on the right andleft threaded screw on the connecting rod z' 2'.

Having thus described my improvements, What I claim as my invention, anddesire to secure by Letters Patent is- The volute spring as set forthwhich increases both in Width and thickness from its center to itscircumference, in combination With a disk of rubber or other elasticmaterial substantially in the manner, and for the purpose specified.

E. G. ALLEN.

Witnesses:

EsAU LINCOLN, JOSEPH Govnrr.

